package com.md.lianxi;

import java.util.Scanner;

public class LianXi04 {
	public static void main(String[] args) {
		Scanner scanner= new Scanner(System.in);
		
		int a=1;
		int b=0;
		while (a<=100) {
			if (a%2==0) {
				b += a;
				
			}
			a++;
		}
		System.out.println(b);
	}

}
